Merge patch series "Improve checks in blk_revalidate_disk_zones()"

Damien Le Moal <dlemoal@kernel.org> says:

blk_revalidate_disk_zones() implements checks of the zones of a zoned
block device, verifying that the zone size is a power of 2 number of
sectors, that all zones (except possibly the last one) have the same
size and that zones cover the entire addressing space of the device.

While these checks are appropriate to verify that well tested hardware
devices have an adequate zone configurations, they lack in certain areas
which may result in issues with potentially buggy emulated devices
implemented with user drivers such as ublk or tcmu. Specifically, this
function does not check if the device driver indicated support for the
mandatory zone append writes, that is, if the device
max_zone_append_sectors queue limit is set to a non-zero value.
Additionally, invalid zones such as a zero length zone with a start
sector equal to the device capacity will not be detected and result in
out of bounds use of the zone bitmaps prepared with the callback
function blk_revalidate_zone_cb().

This series address these issues by modifying the 4 block device drivers
that currently support zoned block devices to ensure that they all set a
zoned device zone size and max zone append sectors limit before
executing blk_revalidate_disk_zones(). With these changes in place,
patch 5 improves blk_revalidate_disk_zones() to address the missing
checks, relying on the fact that the zone size and zone append limit are
normally set when this function is called.

Link: https://lore.kernel.org/r/20230703024812.76778-1-dlemoal@kernel.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 50 insertions, 36 deletions

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index fce9082384d6..da92ce0c5da9 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -448,7 +448,6 @@ struct blk_revalidate_zone_args {
 	unsigned long	*conv_zones_bitmap;
 	unsigned long	*seq_zones_wlock;
 	unsigned int	nr_zones;
-	sector_t	zone_sectors;
 	sector_t	sector;
 };
 
@@ -462,38 +461,34 @@ static int blk_revalidate_zone_cb(struct blk_zone *zone, unsigned int idx,
 	struct gendisk *disk = args->disk;
 	struct request_queue *q = disk->queue;
 	sector_t capacity = get_capacity(disk);
+	sector_t zone_sectors = q->limits.chunk_sectors;
+
+	/* Check for bad zones and holes in the zone report */
+	if (zone->start != args->sector) {
+		pr_warn("%s: Zone gap at sectors %llu..%llu\n",
+			disk->disk_name, args->sector, zone->start);
+		return -ENODEV;
+	}
+
+	if (zone->start >= capacity || !zone->len) {
+		pr_warn("%s: Invalid zone start %llu, length %llu\n",
+			disk->disk_name, zone->start, zone->len);
+		return -ENODEV;
+	}
 
 	/*
 	 * All zones must have the same size, with the exception on an eventual
 	 * smaller last zone.
 	 */
-	if (zone->start == 0) {
-		if (zone->len == 0 || !is_power_of_2(zone->len)) {
-			pr_warn("%s: Invalid zoned device with non power of two zone size (%llu)\n",
-				disk->disk_name, zone->len);
-			return -ENODEV;
-		}
-
-		args->zone_sectors = zone->len;
-		args->nr_zones = (capacity + zone->len - 1) >> ilog2(zone->len);
-	} else if (zone->start + args->zone_sectors < capacity) {
-		if (zone->len != args->zone_sectors) {
+	if (zone->start + zone->len < capacity) {
+		if (zone->len != zone_sectors) {
 			pr_warn("%s: Invalid zoned device with non constant zone size\n",
 				disk->disk_name);
 			return -ENODEV;
 		}
-	} else {
-		if (zone->len > args->zone_sectors) {
-			pr_warn("%s: Invalid zoned device with larger last zone size\n",
-				disk->disk_name);
-			return -ENODEV;
-		}
-	}
-
-	/* Check for holes in the zone report */
-	if (zone->start != args->sector) {
-		pr_warn("%s: Zone gap at sectors %llu..%llu\n",
-			disk->disk_name, args->sector, zone->start);
+	} else if (zone->len > zone_sectors) {
+		pr_warn("%s: Invalid zoned device with larger last zone size\n",
+			disk->disk_name);
 		return -ENODEV;
 	}
 
@@ -532,11 +527,13 @@ static int blk_revalidate_zone_cb(struct blk_zone *zone, unsigned int idx,
  * @disk:	Target disk
  * @update_driver_data:	Callback to update driver data on the frozen disk
  *
- * Helper function for low-level device drivers to (re) allocate and initialize
- * a disk request queue zone bitmaps. This functions should normally be called
- * within the disk ->revalidate method for blk-mq based drivers.  For BIO based
- * drivers only q->nr_zones needs to be updated so that the sysfs exposed value
- * is correct.
+ * Helper function for low-level device drivers to check and (re) allocate and
+ * initialize a disk request queue zone bitmaps. This functions should normally
+ * be called within the disk ->revalidate method for blk-mq based drivers.
+ * Before calling this function, the device driver must already have set the
+ * device zone size (chunk_sector limit) and the max zone append limit.
+ * For BIO based drivers, this function cannot be used. BIO based device drivers
+ * only need to set disk->nr_zones so that the sysfs exposed value is correct.
  * If the @update_driver_data callback function is not NULL, the callback is
  * executed with the device request queue frozen after all zones have been
  * checked.
@@ -545,9 +542,9 @@ int blk_revalidate_disk_zones(struct gendisk *disk,
 			      void (*update_driver_data)(struct gendisk *disk))
 {
 	struct request_queue *q = disk->queue;
-	struct blk_revalidate_zone_args args = {
-		.disk		= disk,
-	};
+	sector_t zone_sectors = q->limits.chunk_sectors;
+	sector_t capacity = get_capacity(disk);
+	struct blk_revalidate_zone_args args = { };
 	unsigned int noio_flag;
 	int ret;
 
@@ -556,13 +553,31 @@ int blk_revalidate_disk_zones(struct gendisk *disk,
 	if (WARN_ON_ONCE(!queue_is_mq(q)))
 		return -EIO;
 
-	if (!get_capacity(disk))
-		return -EIO;
+	if (!capacity)
+		return -ENODEV;
+
+	/*
+	 * Checks that the device driver indicated a valid zone size and that
+	 * the max zone append limit is set.
+	 */
+	if (!zone_sectors || !is_power_of_2(zone_sectors)) {
+		pr_warn("%s: Invalid non power of two zone size (%llu)\n",
+			disk->disk_name, zone_sectors);
+		return -ENODEV;
+	}
+
+	if (!q->limits.max_zone_append_sectors) {
+		pr_warn("%s: Invalid 0 maximum zone append limit\n",
+			disk->disk_name);
+		return -ENODEV;
+	}
 
 	/*
 	 * Ensure that all memory allocations in this context are done as if
 	 * GFP_NOIO was specified.
 	 */
+	args.disk = disk;
+	args.nr_zones = (capacity + zone_sectors - 1) >> ilog2(zone_sectors);
 	noio_flag = memalloc_noio_save();
 	ret = disk->fops->report_zones(disk, 0, UINT_MAX,
 				       blk_revalidate_zone_cb, &args);
@@ -576,7 +591,7 @@ int blk_revalidate_disk_zones(struct gendisk *disk,
 	 * If zones where reported, make sure that the entire disk capacity
 	 * has been checked.
 	 */
-	if (ret > 0 && args.sector != get_capacity(disk)) {
+	if (ret > 0 && args.sector != capacity) {
 		pr_warn("%s: Missing zones from sector %llu\n",
 			disk->disk_name, args.sector);
 		ret = -ENODEV;
@@ -589,7 +604,6 @@ int blk_revalidate_disk_zones(struct gendisk *disk,
 	 */
 	blk_mq_freeze_queue(q);
 	if (ret > 0) {
-		blk_queue_chunk_sectors(q, args.zone_sectors);
 		disk->nr_zones = args.nr_zones;
 		swap(disk->seq_zones_wlock, args.seq_zones_wlock);
 		swap(disk->conv_zones_bitmap, args.conv_zones_bitmap);